Liquid crystal compounds

ABSTRACT

The invention describes nematic compositions for electrooptical devices for modulation of the transmitted or incident light and for the rendition of numbers, symbols and images as orientation in the spectroscopy and gas chromatography. The compositions comprise, liquid crystalline compounds such as dyestuffs and at least one of the compound having the following general formula: ##STR1## wherein ##STR2##

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of the application Ser. No.877,557, now abandoned. The latter application was awarded a filing dateof Aug. 8, 1978.

BACKGROUND OF THE INVENTION

The invention relates to novel nematic liquid crystal compounds forelectrooptical devices for modulation of the transmitted or incidentlight and for the rendition of numbers, symbols and images; further asorientation medium in the spectroscopy and gas chromatography.

It is known that nematic liquid crystal compounds can be rearranged inelectrical fields and are thus useful for the making of electroopticaldevices (M. Tobias. International Handbook of Liquid Crystal Displays1975-1976 Ovum Ltd. London 1976).

Liquid crystals are also highly useful as orientation medium in thespectroscopy in the visible and near UV field, in the nuclear magneticresonance spectroscopy as well as in the gas chromatography (G. Meier,T. Sachmann, J. G. Grabmaier, Applications of Liquid CrystalsSpringer-Verlag, Berlin-Heidelberg-New York 1975).

Heretofore there were used for the mentioned purposes in many cases thesubstituted benzoic acid phenylesters (economic patent No. 86,269 of theGerman Democratic Republic; Steinstrasser, Z. Naturforsch, 27b, 774(1972)). These esters possess a relatively high viscosity which causesundesirably long starting and shut-off times, particularly at lowtemperatures when used in electro-optical devices. The clearing pointsare partly undesirably low and the melting points have values which aretoo high.

OBJECT OF THE INVENTION

The object of the invention is the use of novel liquid crystal compoundswhich possess a high chemical and thermal stability, no color of theirown in the visible spectral range, sufficiently high clearing pointswith adequately low melting point, and low viscosity values. Use is inelectro-optical devices for modulating the transmittant or incidentlight and for rendering numbers, symbols, and pictures, and furthermoreas orientation medium in the spectroscopy and gas chromatography.

SUMMARY OF THE INVENTION

It has been found that nematic liquid crystal compounds can be used forthe purposes later listed which have the following general formulae##STR3## wherein ##STR4##

The uses in electro-optical devices for modulating the transmitted orincident light and for rendition of numbers, symbols and images,furthermore as orientation medium in the spectroscopy and gaschromatography. The compounds have high chemical and thermal stability,have no color of their own in the visible spectral range, have highclear points at sufficiently low melting points and have low viscosityvalues.

By making mixtures, particularly eutectic mixtures, the melting pointcan still further be lowered and at little changed clear points it ispossible to increase substantially the operating temperature ranges. Theconversion temperatures of the compounds of the invention are found inthe following Tables 1 to 3.

By adding dyes in concentration up to 5% the mixtures can be colored andare then useful for electrooptical structural elements on the basis ofthe guest-host effect. As dyes can be used for instance metallic red orindophenol blue.

As liquid crystalline compounds are for instance useful4-n-propyl-cyclohexane-carboxylic acid-4-cyanophenylester or4-methoxybenzoic acid-4-n-hexyloxyphenylester.

EXAMPLES

                                      TABLE I                                     __________________________________________________________________________     ##STR5##                                                                     __________________________________________________________________________                           conversion                                                                              clear                                        No.                                                                              R.sup.1                                                                            R.sup.2                                                                             R.sup.3                                                                            Fp. sm-sm                                                                              sm-nem.                                                                            point                                        __________________________________________________________________________    1  CH.sub.3                                                                           CH.sub.3 O                                                                          H    107 --   --   229                                          2  CH.sub.3                                                                           C.sub.4 H.sub.9 O                                                                   H    81  --   --   197,5                                        3  CH.sub.3                                                                           C.sub.7 H.sub.15 O                                                                  H    81  --   --   187                                          4  CH.sub.3                                                                           C.sub.8 H.sub.17 O                                                                  H    67  --   --   170                                          5  CH.sub.3                                                                           C.sub.4 H.sub.9                                                                     H    73  --   --   159                                          6  C.sub.2 H.sub.5                                                                    CH.sub.3                                                                            H    62  --   --   188                                          7  C.sub.2 H.sub.5                                                                    CH.sub.3 O                                                                          H    80  --   --   245                                          8  C.sub.2 H.sub.5                                                                    C.sub. 4 H.sub.9                                                                    H    66  --   --   180                                          9  C.sub.2 H.sub.5                                                                    C.sub.7 H.sub.15 O                                                                  H    63  --   --   184                                          10 C.sub.2 H.sub.5                                                                    C.sub.8 H.sub.17 O                                                                  H    58  --   --   175                                          11 C.sub.3 H.sub.7                                                                    CH.sub.3 O                                                                          H    94  --   --   245                                          12 C.sub.3 H.sub.7                                                                    C.sub.2 H.sub.5 O                                                                   H    112 --   --   238                                          13 C.sub.3 H.sub.7                                                                    C.sub.4 H.sub.9 O                                                                   H    75  --   --   222                                          14 C.sub.3 H.sub.7                                                                    C.sub.5 H.sub.11 O                                                                  H    67,5                                                                              --   --   214                                          15 C.sub.3 H.sub.7                                                                    C.sub.7 H.sub.15 O                                                                  H    75  --   (7θ)                                                                         203                                          16 C.sub.3 H.sub.7                                                                    CH.sub.3                                                                            H    72-73                                                                             --   --   240                                          17 C.sub.3 H.sub.7                                                                    C.sub.4 H.sub.9                                                                     H    74-75                                                                             --    83  198                                          18 C.sub.4 H.sub.9                                                                    CH.sub.3 O                                                                          H    121 --   --   236                                          19 C.sub.4 H.sub.9                                                                    C.sub.2 H.sub.5 O                                                                   H    104 --   --   231                                          20 C.sub.4 H.sub.9                                                                    C.sub.4 H.sub.9 O                                                                   H    74-75                                                                             --    88  218                                          21 C.sub.4 H.sub.9                                                                    C.sub.5 H.sub.11 O                                                                  H    71-72                                                                             --   110  206,5                                        22 C.sub.4 H.sub.9                                                                    C.sub.7 H.sub.15 O                                                                  H    66-67                                                                             --   126  196                                          __________________________________________________________________________                           conversion                                                                              clear                                        No.                                                                              R.sub.1                                                                            R.sub.2                                                                             R.sub.3                                                                            Fp. sm-sm                                                                             sm-nem.                                                                             point                                        __________________________________________________________________________    23 C.sub.4 H.sub.9                                                                    CH.sub.3                                                                            H    78  --  --    208                                          24 C.sub.4 H.sub.9                                                                    C.sub.3 H.sub.7                                                                     H    82  --   92   206                                          25 C.sub.4 H.sub.9                                                                    C.sub.4 H.sub.9                                                                     H    65  --  115   192                                          26 C.sub.5 H.sub.11                                                                   CH.sub.3 O                                                                          H    97-98                                                                             --  (59)  237                                          27 C.sub.5 H.sub.11                                                                   C.sub.2 H.sub.5 O                                                                   H    103 --  --    236                                          28 C.sub.5 H.sub.11                                                                   C.sub.4 H.sub.9 O                                                                   H    85  (70)                                                                              124   216                                          29 C.sub.5 H.sub.11                                                                   C.sub.7 H.sub.15 O                                                                  H    66  88  150   202                                          30 C.sub.5 H.sub.11                                                                   CH.sub.3                                                                            H    56-57                                                                             --  90    215                                          31 C.sub.5 H.sub.11                                                                   C.sub.3 H.sub.7                                                                     H    78  --  121   209                                          32 C.sub.5 H.sub.11                                                                   C.sub.4 H.sub.9                                                                     H    78-79                                                                             --  136   195                                          33 C.sub.4 H.sub.9                                                                    NC    H    98-99                                                                             --  --    255                                          34 CH.sub.3                                                                           C.sub.7 H.sub.15 O                                                                  C.sub.2 H.sub.5                                                                    47,5                                                                              --  --    88                                           35 C.sub.3 H.sub.7                                                                    C.sub.7 H.sub.5 O                                                                   C.sub.2 H.sub.5                                                                    63-62                                                                             --  --    123                                          36 C.sub.5 H.sub.11                                                                   C.sub.7 H.sub.15 O                                                                  C.sub.2 H.sub.5                                                                    51-52                                                                             --  --    120                                          37 C.sub.6 H.sub.13                                                                   C.sub.7 H.sub.15 O                                                                  C.sub.2 H.sub.5                                                                    44-45                                                                             --  --    116,5                                        38 CH.sub.3                                                                           C.sub.7 H.sub.15 O                                                                  Cl   80  --  --    142                                          39 C.sub.2 H.sub.5                                                                    C.sub.4 H.sub.9 O                                                                   Cl   78  --  --    175                                          40 C.sub.2 H.sub.5                                                                    C.sub.7 H.sub.15 O                                                                  Cl   73  --  --    151                                          41 C.sub.4 H.sub.9                                                                    C.sub.4 H.sub.9 O                                                                   Cl   77-78                                                                             --  --    188                                          42 C.sub.3 H.sub.7                                                                    C.sub.7 H.sub.15 O                                                                  Cl   73  --  --    174                                          43 C.sub.4 H.sub.9                                                                    C.sub.7 H.sub.15 O                                                                  Cl   73-74                                                                             --  --    166                                          44 C.sub.5 H.sub.11                                                                   C.sub.7 H.sub.15 O                                                                  Cl   66-67                                                                             --  --    154                                          __________________________________________________________________________     () monotropic conversion                                                 

                  TABLE II                                                        ______________________________________                                         ##STR6##                                                                     ______________________________________                                                                              clear                                   No.  R.sup.1   R.sup.2   R.sup.3 Fp.  point                                   ______________________________________                                        45   C.sub.2 H.sub.5                                                                         C.sub.2 H.sub.5                                                                         CH.sub.3                                                                              92     142,5                                 46   C.sub.4 H.sub.9                                                                         C.sub.4 H.sub.9                                                                         CH.sub.3                                                                              88   179-180                                 47   C.sub.5 H.sub.11                                                                        C.sub.5 H.sub.11                                                                        CH.sub.3                                                                              76   185                                     48   CH.sub.3  CH.sub.3  H       68-69                                                                              (48)                                    49   C.sub.3 H.sub.7                                                                         C.sub.3 H.sub.7                                                                         C.sub.2 H.sub.5                                                                       47   130                                     50   C.sub.4 H.sub.9                                                                         C.sub.4 H.sub.9                                                                         C.sub.2 H.sub.5                                                                       50-51                                                                              129                                     51   C.sub.5 H.sub.11                                                                        C.sub.5 H.sub.11                                                                        C.sub.2 H.sub.5                                                                       42-43                                                                              133-134                                 52   C.sub.6 H.sub.13                                                                        C.sub.6 H.sub.13                                                                        C.sub.2 H.sub.5                                                                       53   122                                     53   C.sub.3 H.sub.7                                                                         C.sub.3 H.sub.7                                                                         Cl      73   186                                     54   C.sub.4 H.sub.9                                                                         C.sub.4 H.sub.9                                                                         Cl      83   181                                     55   C.sub.5 H.sub.11                                                                        C.sub.5 H.sub.11                                                                        Cl      69-70                                                                              190                                     ______________________________________                                    

                  TABLE III                                                       ______________________________________                                         ##STR7##                                                                     ______________________________________                                                                         conversion                                                                             clear                               No.  R.sup.2    R.sup.4   Fp.    sm-nem.  point                               ______________________________________                                        56   C.sub.4 H.sub.9                                                                          C.sub.4 H.sub.9                                                                         68     --       161                                 57   C.sub.6 H.sub.13                                                                         CH.sub.3  60     --       105                                 58   C.sub.6 H.sub.13                                                                         C.sub.5 H.sub.11                                                                        73     --       146                                 59   C.sub.2 H.sub.5                                                                          C.sub.4 H.sub.9 O                                                                       120    --       141                                 60   CH.sub.3 O C.sub.4 H.sub.9                                                                         110    --       212                                 61   C.sub.2 H.sub.5 O                                                                        C.sub.4 H.sub.9                                                                         108    --       212                                 62   C.sub.6 H.sub.13 O                                                                       H         125    218      255                                 63   C.sub.6 H.sub.13 O                                                                       CH.sub.3  50      63      151                                 64   C.sub.6 H.sub.13 O                                                                       C.sub.4 H.sub.9                                                                         72      82      200                                 65   C.sub.6 H.sub.13 O                                                                       C.sub.4 H.sub.9 O                                                                       66     173      183                                 66   CH.sub.3 O C.sub.4 H.sub.9 O                                                                       110    --       145                                 67   C.sub.2 H.sub.5 O                                                                        C.sub.4 H.sub.9 O                                                                       95     --       150                                 ______________________________________                                    

The following will illustrate the making of the compounds of theinvention and their properties.

A. Reaction Scheme

Compounds where the group X in formula I is ##STR8## are produced byreacting 4-n-alkycyclohexanoylchlorides with the substituted4-hydroxybenzoic acid phenylester according to the following reactionscheme ##STR9##

The reaction is carried out in pyridine at room temperature; apurification of the compounds is obtained by repeated recrystallizationfrom methanol.

EXAMPLE 1

0.02 mol (3.5 g) of 4-ethylcyclohexanecarboxylic acid chloride weredissolved in 20 ml of pyridine. 0.02 mol (6.6 g) of 4-hydroxybenzoicacid-4-heptyloxyphenylester dissolved in 20 ml pyridine were then added.After vigorous stirring the mixture was maintained for 12 to 15 hours ata temperature of +5° C. which caused the formed ester and the pyridiniumchloride to precipitate. The mixture was then poured onto 200 g of icetogether with 8 ml of concentrated sulfuric acid. The precipitate formedwas extracted with ether, washed with a sodium hydroxide solution andwater, dried and concentrated by evaporation. After three-foldrecrystallization from methanol there were obtained 6.5 g=70% of thetheoretical amount of the compound No. 9 of the above table.

The point of the compound was at 63° C. and the clear point was at 184°C.

EXAMPLE 2

In an analogous manner to Example 1 and again to obtain a compoundhaving the group ##STR10## the compound No. 37 of the above table isreacted in pyridine at room temperature. The compound is purified byrepeated recrystallization from methanol ##STR11##

There is obtained a yield of 65%. The point is at 44° to 45° C. and theclear point at 116.5° C.

B. Reaction Scheme

Compounds with the group ##STR12## are made by reaction of4-n-alkylcyclohexanoylchlorides with the 2-substituted hydroquinonesaccording to the following reaction scheme ##STR13##

The reaction is carried out in pyridine at room temperature; apurification of the compounds is obtained by repeated recrystallizationfrom methanol.

EXAMPLE 3

0.04 mol (9.2 g) of 4-n-hexylcyclohexanocarboxylic acid chloride weredissolved in 40 ml pyridine. To the solution (0.02 mol (2.8 g) of2-ethylhydroquinone dissolved in 25 ml pyridine were added. The mixturewas subjected to stirring and was kept for 12 to 15 hours at +5° C.which caused the ester and the pyridinium chloride to precipitate. Themixture was then poured onto 300 g of ice together with 10 ml ofconcentrated sulfuric acid and was extracted with ether. The estersolution was washed with a salt solution and water, dried and subjectedto concentration by evaporation. After three times recrystallizationthere were obtained 6.8 g=65% of the theoretical amount of the compoundNo. 52 of the above table.

The point of the compound was 53° C. and the clear point was at 122° C.

EXAMPLE 4

In analogous manner to Example 3 and also in order to obtain a compoundwith the group ##STR14## the compound No. 47 of the above table isreacted in pyridine at room temperature. The compound is purified byrepeated recrystallization from methanol. ##STR15##

The yield is 68%. The point is at 76° C. and the clear point at 185° C.

EXAMPLE 5

The compound No. 51 of the above table by way of example shows thedynamic scatter effect in the conventional electro-optical devices. At50 Hz alternating voltage a threshold voltage was obtained of U_(o) =7.5V; at direct current the threshold voltage was U_(o) =5.5 V. Goodcontrasts of 20:1 or higher were obtained at voltages which amounted tothe 2.5 value of U_(o). Even with use of voltages up to 60 V nodecomposition phenomena were observed.

EXAMPLE 6

The compound No. 57 possesses positive dielectric anistropy and issuitable for electro-optical devices on the basis of the field effects(Fresdericksz-rearrangement, Schadt-Helfrich-effect, guest-host-effect).In the Schadt-Helfrich-cell (twist-cell) a threshold voltage wasobtained of 4 V/50 Hz; the complete reorientation was obtained at 8 V/50Hz.

EXAMPLE 7

The compound No. 57 was mixed with 1% methyl red and an orientingcomposition was formed with a horizontal layer. Upon transmissionthrough the compound of polarized light the typical absorption band ofthe methyl red was obtained if the polarization plane of the light wasarranged parallel to the preferential direction of the nematic layer. Onthe other hand no absorption was ascertainable if the polarization planeof the light was arranged vertically to the preferential direction ofthe nematic layer. This result of the dichroismus of the dyestuff methylred is based on the specifically directed incorporation of the dyestuffmolecules in accord with the orientation of the nematic matrix. Sincethe compounds of the invention have no absorption in the visiblespectral range they can particularly be used for spectroscopy in thisrange. By means of electrical fields (5 V/50 Hz) the initiallyhorizontal layer is raised up in electro-optical structural elements andthere is thereby a color shift obtained from red to faint pink.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. Nematic composition forelectro-optical devices for the modulation of transmitted or incidentlight and the rendition of numbers, symbols and images, or asorientation medium in spectroscopy and gas chromatography comprisingliquid crystalline compounds, non-liquid crystalline dyestuffs and atleast one compound having the following general formula: ##STR16##wherein R¹ equals C_(n) H_(2n+1) with n being 1 to 9;R² equals C_(n)H_(2n+1) - or C_(n) H_(2n+1) O- when X is ##STR17## and R² equals C_(n)H_(2n+1) O- or --CN when X is ##STR18## R³ equals --CH₃, --C₂ H₅, --Clor --Br; and R and R⁴ each equals C_(n) H_(2n+1) or C_(n) H_(2n+1) O-,with n being 1 to 9 and ##STR19## represents cyclohexyl.
 2. The compoundhaving the formula: ##STR20##